GB2248567A - A lens carrier for use in a lens axis alignment device and in a lens-surfacing machine - Google Patents

Abstract

A lens carrier (20) adapted to support a blocked lens (26) and having locking means (46) for locking the blocked lens on the carrier in a removable manner, is arranged such that the carrier with a blocked lens thereon is pivotally and removably mountable on a lens axis alignment device and is also provided with means (28, 32) whereby it can be supported on a lens-surfacing machine. <IMAGE>

Description

A Lens Carrier for use in a Lens Axis Alignment Device and in a Lens-surfacing Machine This invention relates to a lens carrier for use in a lens axis alignment device and in a lens-surfacing machine, such as a lens grinding, lapping and polishing machine, so as to permit optical retail practices to provide a one-hour service for multifocal lenses, the lenses being specially surfaced using only one machine at the retail point.

Speedy service is becoming the norm for many consumer products such as spectacles. To meet this demand, optical retail practices glaze and fit stock lenses into frames and advertise a one-hour service.

But the provision of multi-focal or varifocal lenses is another story altogether. Approximately 80% of multifocal patients need a cylinder correction, and until recently there was no alternative to sending the Rx away to an optical laboratory for processing. This makes an embarrassing exception to the "one-hour" promise.

A quick look at the existing options for speedy service in retail practice lens-making reveals the need for a high level of investment, either in cash or in experienced personel, to be sure of quality lenses in the short time cycles desirable.

One solution which has been adopted is for a practice to buy thin lens 'wafers' and then to assemble two such wafers together to provide a bi-focal lens according to the prescription. The wafers are bonded with UV sensitive adhesive and cured. Although relatively fast, this method ties the practice to a narrow range of lens forms obtained only from the original supplier. The investment required can be about 8,000.00 at current prices.

Another solution - which originated in the U.S.A. is for the practice to buy equipment which permits it to cast CR39 lenses as they would be cast in a factory.

However, curing such lenses takes at least three hours (with water) or overnight (by air), and an inevitable proportion of rejects will leave some customers still disappointed. Moreover, the equipment requires an investment of about 40,000.00.

The most popular option at the present time, due to the sophisticated machine tools produced by several specialist optical engineering companies and a pool of skilled labour available from existing optical wholesalers, is to use traditional lens-surfacing machines and methods. However, a thousand square feet of floor space, ample power points, water supplies with good drainage and ideally three staff members makes for a major project. An investment of about 50,000 is called for if this option is adopted.

In contrast to all this, the present invention constitutes an entirely new approach to traditional lens surfacing. Thus, the traditional lens-surfacing is reorganised, in accordance with the invention, so that the multifocal lenses are blocked and generated in the factory, leaving only a lens axis alignment device and a single twin-spindle surfacing machine with a set of tools to be installed in the retail unit. This needs only a small working area, without the need for skilled staff, while the investment required can be as low as 8,000.00.

Accordingly, with this aim in view, the present invention is directed, from one aspect, to a lens carrier adapted to support a blocked lens and having locking means for locking the blocked lens on the carrier in a removable manner, in which the carrier with a blocked lens thereon is pivotally and removably mountable on a lens axis alignment device and is also provided with means whereby it can be supported on a lens-surfacing machine.

The invention also extends to a lens axis alignment device which incorporates, as a removable component, the lens carrier described above. The lens axis alighment device can further comprise a protractor and means for pivotally supporting a lens carrier in such a, way that the lens carrier can be rotated with respect to the graduations on the protractor while the lens is aligned at zero degrees before being locked in a particular position on the carrier by the locking means means thereon.

The invention further extends to a lens-surfacing machine which incorporates, as a removable component, a lens carrier as described above.

It is to be noted that the lens is already "blocked" - and the zero degree line marked with respect to the segment or varifocal area - prior to the lens being applied to the lens carrier at the retail practice. In other words, blocking and marking of the lens is carried out at the factory and not at the retail practice.

Examples of a lens carrier, a lens axis alignment device and a lens-surfacing machine in accordance with the invention are shown in the accompanying drawings, in which: Figure 1 is a plan view of one component of a lens axis alignment device in accordance with the invention; Figure 2 is a part-sectional side view of a blocked lens on a lens carrier which is adapted to be pivotally and removably mounted on the component shown in Figure 1; Figure 3 is taken on the line A-A in Figure 2; Figure 4 is a plan view of the blocked lens and lens carrier shown in Figure 2; Figure 5 is a plan view from below of the blocked lens showing the factory markings on its surface; Figure 6 is a plan view similar to Figure 1 showing the lens carrier of Figures 2-4 pivotally mounted on the component shown in Figure 1 in order to form a lens axis alignment device;; Figure 7 is a fragmentary view of a lens-surfacing machine illustrating the way in which the lens carrier and blocked lens of Figures 2-4 are mounted on the machine; and Figure 8 is another fragmentary view of the machine shown in Figure 7 after the lens carrier has been released by a collet forming part of the machine.

The lens axis alignment device will be described first with reference to Figure 1 of the drawings. It is of very simple construction and comprises a rigid base plate 10 of rectangular outline which is adapted to be supported on a firm flat surface such as a table-top. A semicircular groove 12 of shallow form is provided in the flat upper surface of the base 10 so as to receive a semicircular protractor 14 which is provided with graduations extending over 180 . The protractor 14 is made of a transparent synthetic plastics material and is held on the base 10 by screws or other fixing means 16. Concentrically arranged with respect to the geometric centre of the protractor is a circular depression 18 in the upper surface of the base 10.

This depression serves to receive, and to act as a pivotal mounting for, a blocked lens carried by a lens carrier (not shown in Figure 1) which will now be described with reference to Figures 2-4.

The lens carrier 20 is in the form of a yoke in that it comprises a central circular portion 22 having an aperture 24 adapted to receive a blocked lens 26. The carrier has two radially-projecting arms 28 on opposite sides of the central portion 22. As will be seen from Figure 2, the carrier is essentially flat in side view and has bevelled end surfaces 30 on the arms 28. It also has pivot sockets 32 in the outer end portions of the arms 28 to receive locating means on a lens-surfacing machine for grinding and polishing the lens, as well as locating surfaces 34 on the arms to locate the lens carrier accurately on the machine.

The lens axis alignment device is used to align a lens axis in the manner illustrated in Figure 6 where the portion 36 of the blocked lens 26 on the carrier 20 has been received in the depression 18 in the base 10 of the device. As will be seen from Figure 2, the actual lens 38 is carried on a lens block 40 made of a synthetic plastics material which has been moulded in a mould 42 of tinned steel or other metal. So, it is the portion 36 of reduced cross-section on the block 40 and its mould 42 which is actually received in the depression 18 in the base 10 of the lens axis alignment device. This means that the blocked lens and its carrier are turned upside down (as they are shown in Figure 2) before being placed on the base 10.

Prior to the lens being blocked in the factory, the desired zero axis for the lens is marked either on the lens or on a clear plastic film applied to the convex surface of the lens so that the zero axis can be seen clearly through the lens as shown in Figure 5. Once therefore the blocked lens 26 has been mounted on the carrier 20, the latter is pivoted into a position where a mark 29 on the end portion of one of the arms 28 coincides with a desired graduation on the protractor scale. The blocked lens 26 is then rotated on the carrier 20 until the axis line 50 on the lens (see Figure 5) is aligned by means of a graticule with the "0"" " and "180 " markings on the protractor. The blocked lens is then locked against rotation on the carrier by rotation of two locking screws 46 which bear against the larger-section portion 48 of the block 40 and its mould 42.

The lens carrier 20 and the blocked lens 26 thereon can now be lifted off the base 10 and placed in a lens-surfacing machine which is also present at the point of retail sale, the machine having pins or other means which are located in the pivot sockets 32.

The actual construction of the lens-surfacing machine can vary a great deal in practice, but in accordance with the invention the lens carrier 20 carrying the blocked lens 26 is adapted to be mounted as a removable component on the machine so as to be driven by the latter during the lens-surfacing operation. Figures 7 and 8 illustrate a suitable form of machine for this purpose.

Figure 7 shows the lens carrier 20 arranged on the machine in such a way that locating pins 52 on a pneumaticallyloaded arm 62 are able to enter the pivot sockets 32 in the arms 28 of the lens carrier. The lower concave surface 56 of the lens 38 is now brought into contact - by downward movement of a collet 54 - with a diamond-coated toric wheel 58 which is rotated about a shaft 60. In this way the surface 56 of the lens is ground to the correct contour.

As the surface speed is in excess of 5000 feet per minute, this operation normally requires only about 60 seconds.

Figure 8 shows the same machine after the lens carrier 20 has been released by the collet 54. The lens 38 is now held against the toric wheel 58 by the pneumatically-loaded arm 62. The rotation of the toric wheel 58 is now changed to a reciprocating motion and, at the same time, the drive arm 62 is reciprocated as well so as to describe a W-shaped pattern between the lens and wheel surface. At this stage in the operation, a frictionheld lapping or polishing medium is introduced between the lens and the wheel, thereby completing the surfacing of the lens.

It will therefore be seen that the invention provides a retail practioner with the necessary means to make lenses at a capital cost of only 8,000.00 This arises out of the fact that semi-finished multifocal lens blanks are blocked on to an inexpensive disposable lens block in the factory, whereafter the mounted lenses are machined to a spherical curve and correctly, decentred in relation to a reading segment or varifocal area, the lenses being of correct thickness to allow for cylindrical lapping at a retail store.

The blocked lenses supplied by a factory are stocked at the retail store to await the toric prescription. The prescribed lens is then aligned for the Rx axis in the device shown in the drawings of the present application, after which the carrier 20 with the blocked lens 26 thereon is mounted in the lens-surfacing machine shown in Figures 7 and 8 which uses diamond pads, abrasive pads and plain water for the machining and polishing operation. The finished lens is then snapped of the block 40 and its mould 42 - which can be discarded - leaving only checking and edging of the lens before sale.

Claims (15)

Claims

1. A lens carrier adapted to support a blocked lens and having locking means for locking the blocked lens on the carrier in a removable manner, in which the carrier with a blocked lens thereon is pivotally and removably mountable on a lens axis alignment device and is also provided with means whereby it can be supported on a lenssurfacing machine.

2. A lens carrier according to claim 1 which is in the form of a yoke comprising a central portion having an aperture adapted to receive the blocked lens with two arms projecting on opposite sides of the central portion.

3. A lens carrier according to claim 2, in which pivot sockets are provided in the outer end portions of the arms to receive locating means on a lens-surfacing machine.

4. A lens carrier according to claim 3, in which the arms are also provided with locating surfaces in order to locate the lens carrier with accuracy on a lens-surfacing machine.

5. A lens carrier according to any preceding claim, in which the locking means for locking a blocked lens on the carrier comprises one or more screws which engage a peripheral surface of the blocked lens.

6. A lens carrier according to claim 1 substantially as described herein with reference to the accompanying drawings.

7. A lens axis alignment device which incorporates, as a removable component, a lens carrier as claimed in any one of claims 1-6.

8. A lens axis alignment device according to claim 7, in which the lens carrier forming part of the device is pivotally supported on a base provided with a protractor.

9. A lens axis alignment device substantially as described herein with reference to the accompanying drawings.

10. A lens-surfacing machine which incorporates, as a removable component, a lens carrier as claimed in any one of claims 1-6.

11. A lens-surfacing machine according to claim 10 having a pneumatically-loaded arm provided with locating pins which are adapted to locate in sockets provided in the lens carrier.

12. A lens surfacing machine according to claim 10 or claim 11, in which the machine is provided with a toric grinding wheel for grinding a desired contour on a blocked lens mounted, with the lens carrier, on the machine.

13. A lens-surfacing machine according to claim 11 or claim 12 when appendant thereto, in which the pneumatically-loaded arm is arranged for reciprocating movement during one part of the lens-surfacing operation.

14. A lens-surfacing machine according to claim 12, in which the toric wheel is arranged for rotary movement and also for reciprocatory movement.

15. A lens-surfacing machine substantially as described herein with reference to the accompanying drawings.